Solid state lighting devices are used for a number of lighting applications. For example, solid state lighting panels including arrays of solid state lighting devices have been used as direct illumination sources, four example, in architectural and/or accent lighting. A solid state lighting device may include, for example, a packaged light emitting device (LED) including one or more light emitting diode chips. Inorganic LEDs typically include semiconductor layers forming p-n junctions. Organic LEDs (OLEDs), which include organic light emission layers, are another type of solid state light emitting device. Typically, a solid state light emitting device generates light through the recombination of electronic carriers, i.e. electrons and holes, in a light emitting layer or region. LED chips, or dice, can be mounted in many different ways for many different applications. For example, an LED chip can be mounted on a header and enclosed by an encapsulant for protection, wavelength conversion, focusing, dispersion/scattering, etc. LED chips can also be mounted directly to a submount, such as a PCB, and can be coated directly with a phosphor, such as by electrophoresis or other techniques. Accordingly, as used herein, the term “light emitting diode” or “LED” can refer to an LED chip, including an LED chip coated or otherwise provided with phosphor, or to a packaged device, such as a packaged device that includes an LED chip and that provides electrical contacts, primary optics, heat dissipation, and/or other functional features for the LED chip.
Recently solid state lighting systems have been developed for general illumination applications. The design of a solid state lighting system for general illumination typically involves designing optical, power and thermal management systems in order to provide a particular level of performance with respect to lumen output, power requirements and junction temperature of Light Emitting Diode (LED) light sources. The junction temperature of the LEDs may be a significant factor in the lifetime of the LEDs. In particular, if the junction temperature exceeds the recommended junction temperature of the manufacturer, then the LEDs will typically not achieve the expected lifetime. Changes in operating temperature can also result in color shifts in the resulting light output of the LEDs. Thus, maintaining the LEDs at an appropriate junction temperature may be an important consideration in the design of solid state lighting systems. However, as solid state lighting systems may be used in a variety of applications, such as in different fixtures, in different environmental conditions, and/or in different operating regimes, it may be difficult to design solid state lighting systems to account for such varied operating conditions.
The design of thermal management for solid state lighting systems has generally fallen into two categories: passive systems and active systems. Passive systems have typically been integral to the lighting device. For example, the LR6 recessed downlight from Cree LED Lighting Solutions of Morrisville, N.C., utilizes a passive system that incorporates a heat sink that is exposed to the room in which the LR6 is mounted. Thus, the LR6 provides not only the light source but also the trim for a recessed fixture in which the LR6 is mounted. By exposing the heat sink to the room, the LR6 benefits from any air currents that break the boundary layer between the heat sink and the air in the room. Breaking the boundary layer between a heat sink and its environment can increase the efficacy of the heat sink, thereby lowering the junction temperature of the LEDs.
Active thermal management for solid state lighting systems has also been utilized. For example, U.S. Pat. No. 7,144,135 entitled “LED Lamp Heat Sink” describes an LED lamp that includes a fan that moves air over a heat sink. Additionally, LED downlights with integral synthetic jet cooling systems have also been announced. However, current solutions may rely on specifically designed fixtures, structures, and/or environments, which may be inadequate and/or unascertainable to designers and/or manufacturers of the LED modules used in such fixtures, structures, and/or environments.